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The following terms describe mechanisms by which competition occurs, which can generally be divided into direct and indirect. These mechanisms apply equally to interspecific and interspecific competition.

Male-male competition in red deer during rut is an example of interference competition within a species.

Interference competition - occurs directly between individuals via aggression etc. when the individuals interfere with foraging, survival, reproduction of others, or by directly preventing their physical establishment in a portion of the habitat.

Exploitation competition - occurs indirectly through a common limiting resource which acts as an intermediate. For example the use of the resource(s) depletes the amount available to others, or they compete for space.

Apparent competition - occurs indirectly between two species which are both preyed upon by the same predator. For example, species A and species B are both preys for predator C. The increase of species A will cause the decrease of species B because the increase of A's would increase the number of predator C's which in turn will hunt more of species B.

Intraspecific competition occurs when members of the same species vie for the same resources in an ecosystem (e.g. food or nutrients, light or space). For example, two trees growing close together will compete for light above ground, and water and nutrients in the soil. Therefore, getting less resources, they will usually perform less well than if they grew by themselves. Adaptations to such an environment include growing taller (especially in forests), or developing a larger root system.

Interspecific competition may occur when individuals of two separate species share a limiting resource in the same area. If the resource cannot support both populations, then lowered fecundity, growth, or survival may result in at least one species. Interspecific competition has the potential to alter populations, communities and the evolution of interacting species.
An example among animals could be the case of cheetahs and lions; since both species feed on similar prey, they are negatively impacted by the presence of the other because they will have less food. In fact, lions sometimes steal prey items killed by cheetahs.

where r is the growth rate of the population (N), and K is the carrying capacity of its local environmental setting. Typically, r-selected species exploit empty niches, and produce many offspring, each of whom has a relatively low probability of surviving to adulthood. In contrast, K-selected species are strong competitors in crowded niches, and invest more heavily in much fewer offspring, each of whom has a relatively high probability of surviving to adulthood.